Electrical relay-control apparatus



1929- F. ANDORFF ET AL 7 1,723,322 I ELECTRICAL RELAY CONTROL APPARATUSFiled March 8, 1926 I v fix/6735m- 2717 dzzabrflf m? Zarzcbmamz PatentedAug. 6, 1929.

UNITED STATES PATENT OFFICE.

FRITZ ANDORFF, OF VIERNHEIM, AND KURT LANDSMANN, OF MANNHEIM, GER- MANY,ASSIGNORS TO AKTIENGESELLSCHAFT BROWN BOVERI & CIE., OF BADEN,SWITZERLAND, A JOINT-STOCK COMPANY OF SWITZERLAND.

ELECTRICAL RELAY-CONTROL APPARATUS.

Application filed March 8, 1926, Serial No. 93,025, and in Germany March16, 1925.

This invention relates to electrical relay apparatus, particularly tothe type designed to be operated by overloads in the controlled circuit.

The general object of the invention is the provision of apparatuswhereby the tripping time of the relay may be varied withoutnecessitating a corresponding variation in the minimum tripping current.

Another object is the provision of such apparatus in a constructionwhich may be built in small space, which is certain in operation, andwhich is adapted to handle heavy overload currents without danger.

Other and further objects of the invention will be pointed out orindicated hereinafter, or obvious to one skilled in the art upon anunderstanding of the invention.

In the drawing forming a part of this specification we show indiagrammatic fashion a structural arrangement in which the invention maybe embodied, but it is to be understood that this is presented forillustration only and is not to be given any interpretation having theefiect of limiting the invention claimed, short of its true and mostcomprehensive scope in the art.

The drawing is a diagrammatic illustration of relay apparatus embodyingthe invention, arranged to operate a circuit breaker.

Current relays designed to operate with a time la usually involve moreor less complocated constructions in the nature of clockwork, Ferrarisdisc apparatus, or the like, which render the apparatus costly and moreor less susceptible to functional derangements. The simplerconstructions, such as those generally used for protection of motors,etc., of which thermic relays and other delayed action relays areexamples, do not admit of desired variation of the tripping time withoutvariation of the tripping current. By the present invention I makepossible such variation in the tripping time more or less independentlyof the tripping current, so that the tripping time may be lengthened toaccommodate high overloads for a short period, Without necessitating anincrease in the load requisite to trip the relay when such a load iscontinued for a dangerously extended period. One example of theapplication of the invention is in the protection of squirrel cagemotors which have to accelerate large masses on starting, the actionbeing such as to cause an overload conditi on for a starting period ofcomparatively short duration.

The nature of the invention will be understood immediately upon anunderstanding of the illustrative form.

As shown in the drawing, 10 designates the switch or circuit breakerwhich is operated by the relay 11. The time operation of 15 includes theadjustable portion made up Y of two arms m and 'n. which are rotatablymounted on the axis 0 so that either may be swung into or out ofcooperation with the ends of the core member to complete the magneticcircuit of the third limb. The arm in is of greater cross section thanthe arm a, and consequently when positioned to close the magnetic paththrough the limb 15, introduces more iron into the core circuit thandoes arm n. The adjustable arm member may also be moved to a thirdposition, wherein the radius designated I is interposed in the limb 15,thus opening the magnetic path through that limb. As a result of thisarrangement, the amount of iron in the core is variable in threequantities, viz, a maximum quantity when the arm 'lIL is in the corecircuit, an intermediate quantity when arm n is in the core circuit, anda minimum quantity when the limb 15 is open. In the latter instance, theentire core flux passes by way of the limb 14:. The result of thisvariability is a selective variation in the saturation requirements ofthe core, whereby the quantity of secondary current obtainable with agiven primary current may be varied and the rate of increase in thesecondary current relative to a given increase in the rate of theprimary current is likewise varied. The action results from the factthat when the transformer is working at a high saturation an increase inprimary current does not give a proportional increase in secondarycurrent, as compared with operation at a low saturation, the reasonbeing that as the saturation is raised, an increase in proportion of theprimary ampere circuit of the core, a secondary current will notincrease with a given increase of primary turns are required tomagnetize the iron. As a consequence of the arr ngement illustrated,thcreiore, when the arm m 1s in the magnetic current so rapidly as whenthe lesser arm n is in the core circuit. Accordingly, the time requiredfor operation of the relay 11 after the startof the overload in thecontrolled circuit may be varied selectively, the relay being operatedon the same overload in any instance. I a

, The eii ect may also be obtained by other arrangements for varying theleakage reactance of the transformer and in a fashion varying thesaturation. It is a comparatively simple matter to provide anarrangement in which the conditions are such that with any of therelative arrangements, there is no appreciable proportionaldecrease ofsecondary current after some selected limit of primary current isreached. For this purpose it is desirable that, in adjustment, the wholeiron path be not entirely interrupted, for example as shown in thedrawing, wherein it is bridging pos tion.

possible to always maintain a closed iron circuit, the active iron crosssection, however, being varied.

What we claim is:

1. Intransformer apparatus, a. core having an air gap, operating windingmeans disposedon said core, and a member having ditterent reluctancevalues between different pairs of oppositely-disposed points on itsouter surface and being supported for movement in such wise as to placeany one of such pairs of points in said gap to the exclusion of theremainder of such pairs of points.

2. In transformer apparatus, a core having an air gap, operating windingmeans disposed on said core, and a member-comprising arms havingdifferent reluctance values and each being operable to substantiallybridge said gap, said member being supported for movement in such wiseas to provide for movement ofsaid arms selectively into FRITZ ANDORFF.KURT LANDSMANN.

